THE THERMAL-CONDUCTIVITY AND HEAT-FLOW DENSITY OF THE JEANNE-DARC BASIN, OFFSHORE EASTERN CANADA

In an effort to understand the present-day thermal structure of the Je anne d'Arc Basin, we derive matrix thermal conductivity values, using a geometric mean model, from thermal conductivity values of thirteen l ithologic end-members (of which seven are measurements on materials fr om the Jeanne d'Arc Basin) and lithological data. Temperature correcti ons to thermal conductivity are made for both matrix and pore water. I n-situ thermal conductivities were obtained after correcting for the e ffect of porosity, which we estimated from both lithological informati on and digital well logs. Calculated thermal conductivities of the for mations range from 1.46 to 2.65 W m-1K-1. The heterogeneity of formati on thermal conductivity is caused by at least two factors. The first i s lithological variation due to facies change. The second is due to di fferent degrees of compaction. Under-compacted intervals (overpressure zones) are characteristically of lower thermal conductivity. The surf ace heat flow density calculated with an inverse method in seventeen w ells varies from 37.8 to 60.7 mW/m2. This study indicates that surface heat flow density values estimated without porosity corrections may b e 15% higher than those with porosity corrections. We also demonstrate the sensitivity of modelled timing of maturation to thermal conductiv ity estimations.